1. Field of the Invention
The present invention relates to substrate bonding apparatuses and substrate bonding methods, and more particularly, to a substrate bonding apparatus and a substrate bonding method to align and bond two substrates.
2. Description of the Background Art
Recently, the contents of communication/information processing have grown complex from character information into images, sounds and animations, and the need to transmit and process information of large volumes at high speed arises. Therefore, in the field of manufacturing mobile type electronic appliances such as cell phones, notebook-sized personal computers, audio equipments or digital cameras, the mounting technology of semiconductor devices used in the electronic appliances are being improved so as to cope with much higher functionality and further downsizing of the electronic appliances.
In recent years, the mounting technology of semiconductor devices has progressed from the two-dimensional array mounting in which a plurality of semiconductor chips are placed in a planar manner, to a three-dimensional layered mounting in which a plurality of semiconductor chips are sterically layered. Therefore, the wiring between the semiconductor chips has been shortened and the operation speed of the semiconductor devices has been increased, and also the mounting area efficiency of circuit devices mounted on one semiconductor device has been remarkably improved.
Further, in order to improve manufacturing cost performance, as the assembly (packaging) technology of semiconductor devices, not the assembly technology at a chip-level but the assembly technology at a wafer-level has made progress, or more specifically, the technology has made progress in which an assembly process up to re-wiring, encapsulation and terminal processing is performed, without dividing a semiconductor substrate (a wafer), on which a plurality of circuit devices are formed, into individual chips, i.e. in the state of the wafer, and finally the semiconductor substrate is divided into individual chips, and a device is assembled.
Against this background, a substrate bonding apparatus that bonds two substrates such as semiconductor wafers is developed. In this case, the two semiconductor wafers are bonded such that a plurality of electrodes formed on the surfaces of the semiconductor wafers are connected to each other. Accordingly, in the substrate bonding apparatus, the position adjustment (alignment) technology of semiconductor wafers is one of the most important technologies.
Conventionally, as the alignment technology, as is disclosed in the pamphlet of International Publication No. 2005/067046, the method is employed in which the positions of two semiconductor wafers are aligned by detecting fiducial marks arranged on holders that hold the two semiconductor wafers using, for example, a dual-field camera or a dual-field microscope in a state where the surfaces of the two semiconductor wafers are opposed. However, the size of diameter of the semiconductor wafer is increasing to 8 inches, and then to 12 inches, year by year, and therefore in some cases, the positional deviation is generated between a semiconductor wafer and a holder that holds the semiconductor wafer by electrostatic adsorption, in the case such as when the holder to hold the semiconductor wafer is installed on the substrate bonding apparatus. This positional deviation causes alignment error at a level that cannot always be ignored.